How to Validate Addresses

Calculating sales tax? Ditch the ZIPs and get rooftop-level accuracy with Avalara’s API!

Valid addresses are a critical component of accurate tax calculation. I know what you’re thinking – I have the ZIP code, isn’t that enough? Not really. Why? ZIP codes are generally too broad for tax determination because zones are set at the federal level for mail delivery. State and local tax authorities often use other criteria for bounding their tax jurisdictions, such as a special stadium or restaurant tax district.

So, what’s the best way to ensure your organization has up-to-date, roof-top accurate addresses?

An API.

The Address Validation API

AvaTax’s Address Validation API provides rooftop accuracy. This helps you develop a more robust user experience for your customers. In addition, the API helps your organization calculate more accurate taxes, so you can minimize overcharging or undercharging sales tax.

One way AvaTax enables accurate address validation is through the use of the ResolveAddress endpoints for your address resolution and correction needs. Make calls to ResolveAddress early in your order pipeline to help your customer complete their order and limit abandonment. By using AvaTax’s address service, you can have a one-stop shop for your deliverability and tax calculation needs.

Sometimes you get incomplete or mistyped information about an address. AvaTax can often resolve addresses with partial information. Let’s say a salesperson from your organization was on the phone with a customer, and they took down all the necessary information, but for some reason they forgot to write down the ZIP code. They provided you with this address:

14 Lawton Road, Wappingers Falls NY

We will send a GET request (more on this in a moment):

GET /api/v2/addresses/resolve?line1=14%20Lawton%20Rd&city=Wappingers%20Falls&region=NY

The results from both GET and POST API calls contain full information about this address and postal code. We received the correct postal code for 14 Lawton Road, a fully validated postal mailing address, latitude, longitude, and a list of taxing authorities applicable to this location.

The validatedAddresses object displays the corrected address. If the raw address and the validated addresses are the same, then you know you didn’t mistype anything, and you don’t need to correct your user! The validatedAddresses object contains the postal-correct mailing address of the target location. This address object is normalized to postal mailing requirements and can be used for mail sorting.

The coordinates are the best available latitude-longitude measurement of this address.

"resolutionQuality": "Intersection",

The precision available here is measured by the resolutionQuality value; in this case, we didn’t match the exact street number, but instead we matched the nearest intersection.

The list of taxAuthorities provides information about which tax authorities have jurisdiction over this address.

Types of Address Resolution Errors

If your data is just thoroughly incomplete, AvaTax will try its best to find a valid address. Here’s what would happen if you provide virtually no information at all:
POST /api/v2/addresses/resolve

{"line1":"2720 W Main Street"}

In this case, there just isn’t enough information in the address to return a valid result. You’ll get an error message that looks like this:

{"code":"GetTaxError","number":300,"message":"An Address is incomplete or invalid.","description":"","faultCode":"GetTaxError","helpLink":"/avatax/errors/GetTaxError","refersTo":"Addresses[0]","severity":"Error"}

But if you just had an extra bit of information like a postal code, you’d get a good result again. For example, this request produces a correct validation result:
POST /api/v2/addresses/resolve

{"line1":"2720 W Main Street","postalCode":"12590"}

Now, what happens if you only have a rough guess of the location? AvaTax will do its best to provide a useful jurisdiction estimate based on a centroid, but it won’t be able to give you a valid mailing address. In this example, there is only a postal code, country, and region. Here’s the request and result:

POST /api/v2/addresses/resolve

{"postalCode":"98110","region":"WA","country":"US"}

The result shows that we have a rough guess of coordinates, but the resolution quality is low. We consider this a ‘Not Coded’ result. Even though the geocode is somewhat close, we can’t be sure of the actual location they meant. This level of detail might be useful when planning deliveries, but it won’t do for actual shipping – you’ll still have to call the customer back and ask for a full address.

Next, what happens if you provide what looks like a good address, but there’s something wrong with it? If I were to try validating the address “123 Main Street” in Irvine, California, I would get an “Undeliverable address” error. That’s because the Main Street in Irvine begins with street number 1000, and there is no such address as 123 Main. In this case, you’ll need to look at the messages component of the result:

"messages":[{"summary":"The address is not deliverable.","details":"The physical location exists but there are no homes on this street. One reason might be railroad tracks or rivers running alongside this street, as they would prevent construction of homes in this location.","refersTo":"Address","severity":"Error","source":"Avalara.AvaTax.Services.Address"}]

With this information, you should be able to put together address-validation in your user experience. You can show customers map coordinates near to their location easily, and help confirm that your postal code, city name, and region name are correct.

Customers and departments of revenue demand accurate sales tax calculations; they won’t settle for anything less. That’s the minimum barrier to overcome for customer satisfaction, and taxing authorities are making sales tax more complex. Fortunately, with the right sales tax API, you can solve for the critical components that go into accurately calculating sales tax, starting with address validation down to the roof-top level.